U.S. patent application number 13/446846 was filed with the patent office on 2012-08-09 for equipment for quick dispersion of polyacrylamide powder for fracturing operations.
Invention is credited to Peter Nichols.
Application Number | 20120199356 13/446846 |
Document ID | / |
Family ID | 41707506 |
Filed Date | 2012-08-09 |
United States Patent
Application |
20120199356 |
Kind Code |
A1 |
Nichols; Peter |
August 9, 2012 |
Equipment For Quick Dispersion Of Polyacrylamide Powder For
Fracturing Operations
Abstract
A compact and transportable installation, which is quick to
start up and is independent, which allows for dissolution of at
high concentration, in very short periods of time, substantial
quantities of polyacrylamide powder and which is designed to be
used in fracturing operations on gas or oil fields, is provided.
The installation successively includes a polymer storage area, a
vertical polymer transfer hopper, a supply overflow pipe, a polymer
dosing system fed by the pipe, a polymer slicing unit (PSU) type
polymer dispersion device, a tank for storage and degassing of
polymer in solution, and a volumetric pump to inject and dose the
solution of polymer obtained at a suction of a high pressure pump
enabling the fracturing operations.
Inventors: |
Nichols; Peter; (Savannah,
GA) |
Family ID: |
41707506 |
Appl. No.: |
13/446846 |
Filed: |
April 13, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2009/063961 |
Oct 23, 2009 |
|
|
|
13446846 |
|
|
|
|
Current U.S.
Class: |
166/308.1 ;
166/75.11 |
Current CPC
Class: |
E21B 21/062 20130101;
E21B 43/26 20130101; B01F 7/164 20130101; C08J 2333/26 20130101;
B01F 3/1221 20130101; C09K 8/685 20130101; C08J 3/05 20130101; E21B
21/06 20130101; B01F 15/0251 20130101 |
Class at
Publication: |
166/308.1 ;
166/75.11 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 19/00 20060101 E21B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2009 |
FR |
0957308 |
Claims
1. A compact and transportable installation, which is quick to
start up and is independent, which allows for dissolution of at
high concentration, in very short periods of time, substantial
quantities of polyacrylamide powder and which is designed to be
used in fracturing operations on gas or oil fields, said
installation successively including: a polymer storage area a
vertical polymer transfer hopper; a supply overflow pipe; a polymer
dosing system fed by said pipe; a polymer slicing unit (PSU) type
polymer dispersion device; a tank for storage and degassing of the
polymer in solution; and a volumetric pump to inject and dose the
solution of polymer obtained at a suction of a high pressure pump
enabling the fracturing operations.
2. An installation according to claim 1 wherein the polymer
dispersion device is a screw batcher with a flow rate of 100
kg/h.
3. An installation according to claim 1 wherein the polymer
dispersion device is a screw batcher with a flow rate of 300
kg/h.
4. A hydraulic gas or oil well fracturing process comprising the
step of injecting a mixture of fracturing water/polyacrylamide in
solution, implementing the installation of claim 1.
5. The process according to claim 4 wherein the polyacrylamide has
a molecular weight of at least 10 million.
6. The process according to claim 4 wherein the polymer dispersion
is done at a concentration of at least 10 g/l, in less than 10
minutes with a polyacrylamide flow rate of 100 kg/h.
7. The process according to claim 4 wherein the polymer dispersion
is done at a concentration of at least 10 g/l, in less than 10
minutes with a polyacrylamide flow rate of 300 kg/h.
8. The process according to claim 4 wherein a storage time of the
polymer is between 10 and 20 minutes.
9. The process according to claim 4 wherein the injection of the
fracturing water/polyacrylamide in solution mix is performed at a
pressure between 50 and 600 bars.
10. The process according to claim 5 wherein the polyacrylamide has
a molecular weight of at least 15 million.
11. The process according to claim 8 wherein the storage time of
the polymer is approximately 15 minutes.
12. The process according to claim 9 wherein injection of the
fracturing water/polyacrylamide in solution mix is performed at a
pressure of about 400 bars.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of pending
International Patent Application PCT/EP2009/063961, filed Oct. 23,
2009, which designates the United States and claims priority from
French Patent Application 0957308, filed Oct. 19, 2009, the content
of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Gas production from clayey shale reservoirs (schist) which
has been a growing method for several years requires fracturing of
the reservoirs to ensure cost-effective gas production.
BACKGROUND OF THE INVENTION
[0003] The reserves in this sector are huge and over extremely
large areas formerly not recoverable such as coal streaks, fine
sand or schist. In the USA, these unconventional resources
increased from 28% in 1998 to 46% of the total natural gas produced
in the USA. The main huge basins are known as Barnett Shale,
Fayette Ville Shale, Mowry Shale, Marcellus Shale, etc.
[0004] The production techniques have often evolved from vertical
wells to horizontal wells, reducing the number of production wells.
However, in all cases, the permeability is insufficient to
naturally produce a quantity of gas making the operations
cost-effective.
[0005] The permeability and production areas therefore need to be
increased by way of stimulation operations and fracturing in
particular.
[0006] Hydraulic Fracturing
[0007] Hydraulic fracturing is designed to create an additional
level of permeability and an increased gas production surface
areas. Indeed, low permeability, natural barriers of compact
layers, impermeability due to drilling operations greatly limit
production.
[0008] These fracturing operations started in 1960 in the
Appalachian Mountains and today over one million operations have
taken place in the USA.
[0009] Engineering, design and implementation technologies have
become increasingly sophisticated and require equipment enabling to
perform these operations in shorter times with detailed analysis of
the results.
[0010] Specific simulators are capable of forecasting very accurate
results.
[0011] Fracturing Operation
[0012] These operations involve injecting high pressure water at a
very high flow rate to create fractures within the production
wells.
[0013] When the fractures are open, sand or beads of a particular
size are injected to prevent these fractures from closing and to
maintain the production surface areas thus created.
[0014] The injection water usually contains a significant amount of
additives, each with a defined function. Generally speaking, the
injected composition includes: [0015] clay swelling inhibitors such
as potassium chloride [0016] biocides to prevent bacteria,
particularly sulphate-reducing bacteria, from developing and
capable of forming viscous masses reducing the injection areas.
Aldehydes are the most commonly used biocides as glutaraldehyde,
acrolein, etc. . . . [0017] oxygen scavengers such as ammonium
bisulphite to prevent the destruction of other components due to
oxidation and corrosion of the injection lines, [0018] corrosion
inhibitors to protect the lines from oxidation by residual
quantities of oxygen. Preference is given to N, n
dimethylformamide, [0019] lubricants such as petroleum distillates,
[0020] gelling agents such as guar gum and hydroxyethyl cellulose,
[0021] iron-chelating agents such as citric acid, EDTA,
phosphonates, [0022] scale control products such as phosphates,
phosphonates or ethylene glycol, [0023] friction reducers to reduce
the pressure drop in turbulent media and significantly increase the
flow rate for the same power and pipe diameter.
[0024] Acid treatment is often performed before or during injection
to treat cementation residue or to dissolve part of the rock in
place in order to provide better access to the field. The sand
injected is of a particular size, usually between 40 and 100
mesh.
[0025] Friction Reducer
[0026] The drag reduction (friction reduction) phenomenon in
turbulent flow was discovered by B. A Toms in 1946 ("Toms effect")
even though previous descriptions ascertained that certain
additives seemed to enhance high speed flows.
[0027] These products are therefore used to reduce pressure drop in
line.
[0028] When the medium is made up of hydrocarbons, oil-soluble
polymers are used, particularly polymethyl methacrylate or
carbohydrate polymers.
[0029] When the medium is water, very high molecular weight
polymers such as polyacrylamides and ethylene oxide polymers are
used. Preference is generally given to polyacrylamides for cost and
sourcing reasons.
[0030] Polyacrylamides
[0031] Initially developed for flocculation applications (water
treatment, mineral treatment, paper mills, etc), polyacrylamides
are increasingly used in other applications, and especially where
their thickening effect on water based system is desired.
[0032] This development is of particular interest for Enhanced Oil
Recovery, Cosmetics and Thickeners for textile printing, etc.
[0033] In the description hereinafter and the subsequent claims,
the generic term of polyacrylamides covers acrylamide homopolyers
as well as all the copolymers containing both acrylamide and other
monomers such as: [0034] acids such as (metha)acrylic acid, AMPS
(2-Acrylamido-2-methylpropane sulfonic acid), etc [0035] cationic
monomers such as the ammonium salts of trimethylethyl methacrylate,
diallyl dimethyl ammonium chloride, etc
[0036] These polymers can be modified by: [0037] branching with
branching agents in sufficiently low quantities to maintain the
solubility [0038] Hydrophobic monomers giving associative polymers
[0039] Monomers with both anionic and cationic charges (zwitteronic
monomers) [0040] Associations of anionic and cationic monomers
(amphoteric), etc [0041] Monomers giving comb polymers.
[0042] The Person skilled in the art is well aware of these sets of
products described in numerous patents.
[0043] For friction reduction, the polymers used must have the
highest molecular weight possible while keeping very good
solubility.
[0044] The polymer of choice is an acrylamide sodium acrylate
copolymer (70% 30% molar ratio) with a molecular weight close to 20
million.
[0045] For their ease of handling, reverse emulsions (W/O) of these
polymers are used with a concentration of active matter between 20
and 50%. These emulsions are stable in storage for about 6 months
and dissolve very quickly (few minutes) in water under
stirring.
[0046] They allow an in line injection in the fracturing water
before the high pressure pump and are practically fully dissolved
in a few minutes both immediately and in the injection line.
[0047] The quantities of polymers injected can be between 250 and
2,000 ppm of active matter and the fracturing time between 2 and 15
hours with several stages of injections (2 to 20).
[0048] The use of emulsions is today generalised over the entire
territory of USA-Canada-Mexico and is spreading into other
countries according to new reserves to be exploited.
[0049] Powder Polyacrylamides
[0050] Environmental pressure has become increasingly strong both
in terms of the water used for this operation and the water
produced.
[0051] The constant demand is to only consume the water from the
field and to treat the water produced which is made up of 60 to 80%
of the water injected.
[0052] The use of powder polymers avoid injecting both hydrocarbons
and surface active agents to be treated in the water produced.
SUMMARY OF THE INVENTION
[0053] The problem to be solved is then how to dissolve substantial
quantities of polymers in short periods of time, i.e. 0.5 to 5
tonnes of polymers in 4 to 10 hours with quick start up (10 to 30
minutes).
[0054] Using standard dispersion equipment with dispersion with an
ejector, a wetting shovel or a spray of water around a pneumatic
transport system, the concentration of mother solution reach a
maximum of 5 g/litre. Furthermore, it is not possible to design
operations requiring for discontinuous dispersions which would
involve volumes of several hundreds of m.sup.3 to be stored with
operation times of 3 to 4 hours.
[0055] It was therefore necessary to find way allowing very quick
in line dispersion of substantial quantities of polymer at a very
high concentration while reducing as much as possible the size of
the equipment which must be transportable, i.e. small enough to fit
on the platform of a truck.
[0056] To do this, the Applicant has engineered a compact and
transportable installation, quick to start up and independent,
allowing to dissolve at high concentration, in very short periods
of time, substantial quantities of polyacrylamide powder and
designed to be used in fracturing operations on gas or oil fields
whereby the installation successively includes: [0057] a polymer
storage area [0058] a vertical polymer transfer hopper [0059] a
supply overflow pipe feeding [0060] a polymer dosing system fed by
the above pipe [0061] a polymer dispersion device including: [0062]
a polymer wetting cone connected to a primary water inlet circuit
[0063] at the lower end of the cone: [0064] a dispersed polymer
slicing and discharge chamber including: [0065] a rotor driven by a
motor and equiped with blades [0066] a fixed stator made up of
evenly spaced plates [0067] over all or part of the periphery of
the chamber, is a ring supplied by a secondary water circuit, the
ring communicating with the chamber so as to ensure the spray of
pressurised water over the plates of the stator thereby allowing
for the release of the sliced and swollen polymer at the surface of
the said plates [0068] a tank for storage and degassing of the
polymer in solution [0069] a volumetric pump to inject and dose the
solution of polymer obtained at the suction of the high pressure
pump enabling the fracturing work.
[0070] Such an installation is sufficiently compact to fit in a
container, on the platform of a truck.
[0071] Obviously, the quantity of polymer to be dissolved would
vary according to the capacity of the well to be fractured. The
bags of powder are stored at the rear of the platform. In practice,
this relates to bags of 25 kg for low capacities or 750 kg for
higher capacities.
[0072] When the powder is stored in bags of 750 kg, the
installation is, in this case, equipped with a bag hoisting system
and a hopper and an additional horizontal transfer screw, preceding
the vertical hopper and into which the contents of the bags is
poured.
[0073] According to the invention, the dosing system is a screw
feeder allowing a flow rate in practice of 100 or 300 kg/h
according to the equipment used.
[0074] In order to convey the polymer from the hopper into the
doser, the installation is equipped with an overflow pipe of a
diameter of 100 to 200 mm according to the equipment used.
[0075] A dispersion device similar to the one used in the invention
has been described by the Applicant in document WO 2008/107492
incorporated by reference, for Enhanced Oil Recovery (EOR) or
flocculation applications.
[0076] The Applicant observed that through few modifications, along
with the above-mentioned information, this device called PSU
(Polymer Slicing Unit) could be adapted to fracturing.
[0077] It is therefore practically possible to use powder
polyacrylamides of different particle sizes for fracturing
operations.
[0078] The polyacrylamide has a molecular weight of at least 10
million, preferably more than 15 million.
[0079] The specifications of the PSUs which can be used for this
invention are summarized in the following table:
TABLE-US-00001 TABLE 1 Specifications of the slicing unit PSU 100
PSU 300 Cutting diameter in mm (size of rotor) 100 200 Number of
fixed blades 50 90 Height of fixed blades in mm 16.6 16.6 Maximum
spacing between blades 700 700 microns microns Spacing between
fixed/rotating blades 100 100 microns microns Cutting angle
2.degree. 3.degree. Number of rotating blades (i.e.: on the rotor)
4 6 Rotor speed 5,000 rpm 3,000 rpm Motor power rating 3 kW 7.5 kW
Dispersion specifications Maximum primary water flow rate 3
m.sup.3/h at 10 m.sup.3/h at 25.degree. C. 25.degree. C. Maximum
flow rate of anionic polyacrylamide 100 kg/h 300 kg/h (anionicity:
30%; molecular weight: 19 millions; particle size: 0-1000 microns)
Maximum secondary water flow rate in the 8 m.sup.3/h at 20
m.sup.3/h at concentric ring surrounding the stator 25.degree. C.
25.degree. C. (pressure: 4 bars) Final concentration of powder
dispersion 10 g/l 10 g/l in water greater than Final pressure 1 bar
1.5 bar dispersion time to obtain the maximum usual <10 min
<10 min viscosity at 40.degree. C.
[0080] The polymer in suspension obtained at the outlet of the
dispersion device (PSU) is then stored in a vertical tank, also
used for degassing, and with an effective volume of between 1 and 5
m.sup.3 according to the volume to be injected. The tank is in
general fitted with a low level gauge and a high level gauge to
prevent unwanted tripping or stopping of the PSU according to the
demand.
[0081] The storage time of the polymer suspension in the tank is
between 10 and 20 minutes, advantageously approximately 15
minutes.
[0082] The invention also relates to a hydraulic gas or oil well
fracturing process by injection of fracturing made of fracturing
water/polyacrylamide in solution, implementing the installation
described above and providing a significant drag reduction
effect.
[0083] The injection of the fracturing water/polymer mix in
solution into the rock is performed at pressure between 50 and 600
bars, advantageously approximately 400 bars.
[0084] The invention shall be made apparent from the following
examples of embodiments supported by the appended figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0085] FIGS. 1a and 1b are a schematic representation of the
dispersion installation of the invention according to the
embodiment described above for bags of 750 kg with a PSU 300.
[0086] FIGS. 2a and 2b are a schematic representation of the
dispersion installation of the invention according to the
embodiment described above for bags of 25 kg with a PSU 100.
DETAILED DESCRIPTION OF THE INVENTION
Example 1
[0087] A fracturing operation is to be performed in the following
conditions:
[0088] instant flow rate: 15 m.sup.3/min, (900 m.sup.3/h)
[0089] diameter of pipe: 6 inches
[0090] injection speed: 13.7 m/sec,
[0091] number of successive injections: 5
[0092] polymer concentration: 300 ppm,
[0093] total fracturing time: 13 hours.
[0094] 270 Kg/hour of polyacrylamide must therefore be injected
over a total time excluding stops between phases of approximately
10 hours i.e. approximately 3 tonnes of powder.
[0095] The equipment must be as compact as possible to fit on the
platform of a truck of 12 m.times.2 m30 H=3 m.
[0096] The construction chosen is made up according to FIGS. 1a and
1b of: [0097] a rail with (1) with a hoist to unload big bags of
750 kg (4 big bags for one operation) [0098] a hopper (2) under the
big bag with a horizontal screw, O150, pitch 150 mm, at a speed of
100 rpm [0099] a vertical hopper (3) with a screw O200, pitch 200
mm, speed: 80 rpm to bring the powder fed by the previous screw
into the hopper [0100] an overflow pipe of O150 (4) supplying a
screw feeder with a flow rate of 300 kg/h [0101] a PSU 300 (5) as
described in document WO 2008/107492, supplied at the top point at
a flow rate of 5 m.sup.3/h and at the lower point at 10 m.sup.3/h.
In order to increase the dispersion speed, the space between the
cutting blades is reduced to 500 microns and the rotor speed is
increased to 4,500 rpm [0102] the suspension obtained in the
dispersion device is sent into a vertical tank (6) used for
degassing giving a holding time of 15 minutes, i.e. effective
volume of 4 m.sup.3 and total volume of 5 m.sup.3 equipped with a
high level gauge and a low level gauge stopping and starting the
dispersion device according to the product demand. This storage
time allows for the installation to be started up in less than 20
minutes [0103] a Moineau pump (7) with a flow rate of 15 m.sup.3/h
equipped with a variable speed control allowing for variation of
this flow rate and controlled by the central control department
which determines the quantity used according to the head loss found
[0104] this Moineau pump is connected to the suction of the main
injection pump of the fracturing system.
[0105] By varying the flow rate of the volumetric pump injecting
the polymer solution, one finds that the same result on the
improvement of the injection of pressure is obtained as with an
emulsion.
[0106] That is, in this case, with a field pressure of 110 bars,
the total injection pressure is of 265 bars in both cases. Without
the polymer the pressure would be approximately 420 bars.
Example 2
[0107] For small capacity operations, a PSU 100 type dispersion
device can be used allowing for a flow rate of a solution at 20
g/litre of 5 m.sup.3/h and a powder flow rate of 100 Kg/h.
[0108] For operations over 10 hours, the quantity of polymer to be
stored will be 1,000 kg, brought in bags of 25 kg.
[0109] The installation would include: [0110] a mixer hopper (1)
with central vertical screw of 2 m.sup.3. The bags are emptied into
a cone at the base of the hopper and the product is introduced into
the hopper by the vertical screw [0111] an overflow pipe (2) of
O100 supplying a screw feeder at a maximum flow rate of 100 kg/h
[0112] a PSU 100 (3) to put 100 kg of polymer per hour into
suspension in a volume of water of 5 m.sup.3 giving a concentration
of 20 g/litre. This dispersion device is equipped with cutting
blades spaced 500 microns apart, at a speed of 4,500 rpm [0113] A
degassing tank with effective volume of 1.25 m.sup.3 (4) with a
holding time of 15 minutes providing start up in a very short time
of less than 15 minutes. This tank is equipped with a low and high
level gauge to start up or stop the dispersion device according to
the demand [0114] a Moineau pump (5) with a flow rate of 5
m.sup.3/h with variable speed control enabling injection of the
solution at the suction of the Triplex fracturing pump.
[0115] The injection is performed via a 4-inch pipe with a flow
rate of 200 m.sup.3/h and a concentration of 500 ppm.
[0116] Two wells are treated on the same site: one with an emulsion
of 70-30 acrylamide/acrylic acid molar mass, of molecular weight of
18 million, at a concentration of 30% active matter, the other with
a powder of the same specifications but with a 10% moisture
content.
[0117] The pressure at the well bottom is 95 bars. With 500 ppm of
active matter, it is observed that the injection pressures to
obtain a flow rate of 200 m.sup.2/h are 190 bars for the emulsion
and 185 bars for the powder.
* * * * *